Photogrammetric projection machine



May 15, 1951 H. T. KELsH 2,552,975

EHOTOGRAMMETRIC PROJECTION MACHINE Filed April 1:5, ,1949.

3 Sheets-Sheet 1 ATTOQNEY Patented May 15, 1951 PHGTOGRAMMETRIC PROJECTION IVILCHINFE Harry l'elsh, Washington, n, Q

Application- Apri-L13, 1949, serial' No. 81,298.

10. Claims.

This. invention relates to.v photogrammetric de.- vices, and is more particularly concerned with an apparatus or machine which.. is used to project stereoscopic pairs of diapositives taken by an aerial camera for the purposeV of making= planimetrie and. topographic maps..

It is. generally understood in this. art, that, the lenses.l employed in. such cameras; and'. in the lenses. of stereoscopic. projectors. have. certain imperfections which produce distortion in. the projected image. These distortions, vary with each lens. Although attempts have been made by the. manufacturerof. such lensesv such. as. the metrogon lenses, it. has. not. been possible.. here.- tofore to produceaperfect lens or. one. which has no distortion characteristics. The distortion may result in certain areas, ot the projected image. having their'elements. spaced. apart to. a greater relative extent. than the, natural, objects photographed. Other distortions. may result in other areas of a. photograph, having their ele.- ments spaced too closely together.. Both. types of distortion may exist in. a. single lens. and no. satisfactory method-v of compensating for such distortions. has. yet been found.

It is an object of this invention to provide a projection machine. of the. type, mentioned, wherein certain distortions,l referred to generally as radial distortionsv as. distinguished from tangential distortions, in the diapositives. produced by the, lens are automatically compensated. My invention is described hereinafter in com,- bination. with the type. of projectingI apparatus disclosed. in my co-pending application for patent, Serial No. 3,263', filed. January 20 19.48, now Patent. No. 2,492,870, dated December 27, 19.49,. and comprisesA certain improvements. therein,. hereinafter more. fully explained.

In the accompanying. drawing there is. illus? trated an embodiment of my invention in which:

Figure 1 is an isometricview of the whole machine- Figure 2 is an isometric view of one of the lens mounts of the machine..

Figure 3 is a side elevational view, of the lens moving linkage..

Figure 4 is. a section along the line 4-4- of Figure 3.

Figure 5 is a side elevational View of the mech;- anism shown in Figure 3.

. Figure. 6 is a plan view of the mechanism of Figures 3 and 5.

Referring with more particularity to the drawing in which like numerals;A designate like parts, the embodiment illustrated comprises, ingeneral,y

CFI

a. suitable frame. structure Igt which is. mounted on adjustable legs. I2f,. and. supported on a. table lf3- orr other suitable. horizontal support. At. the top. of" the frame' IVI,. there` are mounted tracks I4, Which.- carry a pair of optical` projection units indicatedv gener-allyv at I5.v

Each. projection, unit. includes a base member IIv andan inner adjustable block I'I containing an annular rotatable.; flange. Il'8.; recessed in its top, which receives the: lower end or a hood-like member Ii9 in the form or a hollow inverted truncated pyramid. The top.` of] the member I9 is adapted to. carry the. diapositive. 20 Whose images' are to. be projected. A projector 2| of a narrow cone of light; rays, is` movably mounted above the. diapositive 2.0. onv the. upper endV of a gooseneck arm. 2.2. The lower end of the. gooseneck; arm extends around. the member |19, and is secured beneath to av tubular member 23, axially aligned with the projector ZI.t and the node or nodal?. region of the lens of the uni-t hereinafter more fullyy described.

The member 23 is secured to the upper end of a telescopable arm 24. The lower end of arm 24 is secured byA universal joint 25. to one side of',- the platen 26; ofl a tracing. or mapping table 21 ofV the type usually employed in projection plotters', details ofY which are fully disclosed in said copending application. The purpose is. to maintain the point.. sources of light in a converging relationship relative to platen 26l to in- Sure always a. proper stereoscopic projection and limit the light projection through the diapositives 20 to. about the. areav of the platen. This permits concentration of light at the particular area, being mapped. Also, the movementsv of eachj light projector 2l is constrained to positions substantially equidistant from the nodal region of the lens. system of. its corresponding projection unit.

The member 23y is. supported for universal movement by being secured to the. lower end of yoke. arms. 28. and 2.9,v the upper ends of which are pivoted to a gimbal ring 30. by means of pins 3l and 32. The gimbal ring is, in turn, pivotally supported on the block I'I by means of pins 3.3 and 34..

Above the member 23. is disposed a bridge member 35, the. ends of which are secured to the block Ilv by arms 3,6. The bridge 35 is. provided with a vertical flanged aperture. 3l aligned with the axis of the member 23. Within the' aperture 3,1 there is. slidably mounted in a vertical direction a tubular lens barrel 38, carryinga lens system 38A.. and having at itsupper end an outward horizontal flange 39. A plurality of vertical pins 40, 4I and 42 are slidably mounted through the Vflange 39 in spaced relation equidistantly from V41, and 48 are disposed between said heads, re-

spectively, and the upper surface of the flange 39 so as to urge the lens barrel 33 downwardly in the aperture 31. l

On one side of the aperture 31 there is provided through the bridge member 35 an annular seat 49 having a spherical segment surface diverging upwardly and which is adapted to support a ball member 58. The lower surface of the ball member 53 i's spherical and free to move on the seat 49. The upper end of the ball is provided with a special contour or cam surface 5I hereinafter more fully explained. A cam follower 52 in the form of a vertical pin having a Vball point at its lower end engages the top of the ball member 5i] substantially as shown. Said follower 52 is secured to the web 53 of a U-shaped member 54 by means of a lateral displacement spider 55. The parallel arms 56 and 51 of the member 54 are pivoted at the opposite end to posts 58 and 59 by means of pins 60 and 5l, said posts being secured to the bridge member 35.

Projecting outwardly from the lens barrel 38 across a diameter parallel to the axis of the pins 6B and 3 l, are pins 52 and 53, which rest in notches 64 and 65 in the arms 56 and 51. By these means, the springs 46, 41 and 48 hold the ball point of the follower 52 in constant engagement with the ball member 50. As the ball member moves, depending upon the contour of its upper portion 5I, the ball lpoint rises and falls and causes the lens barrel 38 also to rise and fall a corresponding distance as determined by the leverage of the U-shaped member 54.

The ball member 5B is moved by means of a depending arm or rod 68 having one end secured to the bottom thereof and the other end of the rod pin-connected at 31 Vto the outer end of a yoke 68. The arms of the yoke member straddle the tube 23 and are pivoted to the tube by means of pins 69 and 1B across a diameter of the tube y v23 parallel to the aXis of the pins 3| and 32.

In operation, as the mapping table 21 is moved about the mapping surface of the table i3, Vthe tubular members 23 are moved in coordination bythe rods 24 and carry the light projectors 2i with them. The movement of the tubes 23 causes the ball member 5B to rock or tilt in its seat 49 and to move in angular relation corresponding to the movement of the tubes 23 due to the parallel linkage defined by the rod 56, yoke 58, tubes 23 and bridge 35. The contour of the uppersurface of the ball 5U is so designed as to move the follower 52 and hence the lens barrel 33, so as to compensate for the distortional errors of the lens of the camera from which the diapositives were made. The radial distortion characteristics of the lens of the camera and/or the projection lenses arev Vfirst determined by known methods. The results are tabulated for all angles as horizontal displacement from the center or vertical aXis ofthe lens. This horizontal displacement, for example, in the usual wide angle aerial lens increases on the aerial negative from zero to approximately 0.12 millimeters at about 30 to 35 from the central axis. Itv then falls oif rapidly the imagepoint on the diapositive.

4 to zero at 42 and minus 0.15 millimeter at 45. This distortion can be compensated if the lens is moved vertically in an amount equal to the horizontal displacement error of any given image point multiplied by the cotangent of the angle between the vertical axis of the lens and a line passing through the nodal point of the lens and When the displacement error is outward, the lens is moved downward to increase the distances between the diapositive and the lens and vice versa.

I claim:

1. In a vstereoscopic projection apparatus, a projection unit having a diapositive mount, a movable light beam projector, means for moving said projector relative to the diapositive, a projection lens mounted for vertical movement, a linkage system connecting said projector to said lens, said system including a ball cam, a socket for tiltably supporting said cam, links connecting said cam to said projector, a pivoted lever connected to said lens, and a cam follower carried by said lever and slidably engaging said ball cam.

2. In a steroscopic projection apparatus, a projection unit having a diapositive mount, a movable light beam projector, means for moving saidvprojector relative to the diapositive, a projection lens mounted for vertical movement, a linkage system connecting said projector'to said lens, said system including a ball cam, a socket for tiltably supporting said cam, links connecting said camto said projector, a pivoted lever connected to said lens, a cam follower carried by said'lever and means for urging said cam follower in contact with said cam. A

3. In a stereoscopic projection apparatus, Aa projection unit having a diapositive mount, a movable light beam projector, means for moving said projector relative to the diapositive, a projection lens mounted for vertical movement, a linkage system connecting said projector to said lens, said system including a ball cam, a socket for tiltably supporting said cam, links connecting said cam to said projector, a pivoted lever connected to said lens, and a cam follower carried by said lever, means for urging said cam follower in contact with said cam, and means for adjusting the position of said cam follower on said cam.

4. In a stereoscopic projection apparatus, a

pair of projector units having each a diapositive mount and a movable light beam projector, a horizontally movable tracing table having a platen vertically movable thereon, means connecting said platen to said light projectors so as tol direct the light therefrom in a convergent relationship on said platen, a projection lens mounted for vertical Vmovement between said platen and each light projector, and a linkage system for moving each of said lenses predetermined vertical amounts when said table moves from one horizontal position to another and when said platen movesrfrom one vertical position to another. 5. A device as defined by claim 4 in which the light projector of each projection unit is disposed so as to project a beam of light through the nodal region of the lens of its corresponding unit.

6. In a stereoscopic projection apparatusga projection unit having a diapositive support,Y a movable light beam projector on one side and a projector lens on the vother side of said support, said lens being mounted for movement to and from said support, means for constraining the movement of said light beam projector so that for different positions thereof its line of lprojection will pass through the projection lens and through different portions of a diapositive on said support, and a mechanical linkage connecting said lens to said projector to cause said lensto move to and from the support in relation to the movements of 'the light beam projector in an amount to substantially compensate for radial distortion in a diapositive image projected through the lens.

" 7. A device as defined by claim 6 in which the mechanical linkage system includes a cam and a cam follower. i

- r8. l structure as defined by claim '7 having yieldable means for urging the cam follower in contact with the cam.

9. A device as defined by claim 6 in which the mechanical linkage system includes a cam connected to the projector and a cam follower connected to the lens.

10. In a stereoscopic projector apparatus having a: pair of projection units, each unit having a diapositive support, a movable light beam projector on one side and a projection lens on the other side of said support, said lens being mountedv for movement to and from its corresponding REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,247,402 Hopkins Nov. 20, 1917 1,655,306 Barr et al. Jan. 3, 1928 1,713,498 Cooke May 14, 1929 1,980,981 Cooke Nov. 20, 19534 2,085,498 Horner June 29, 1937 2,123,510 Leitz et al. July 12, 1938 2,200,594 Diggns May 14, 1940 2,451,031 Kelsh Oct. 12, 1948 

